Many display devices such as liquid crystal display devices (LCDs) need a flexible printed circuit board (FPC) to connect a variety of electronic circuits together.
Referring to FIG. 6, a typical display device 1 includes a display panel 10, a driving circuit 11 and an FPC 12. The display panel 10 includes a front substrate (not labeled) and a rear substrate (not labeled) substantially abutting the front substrate. A plurality of conductive lines 101 are located on a surface of the rear substrate that faces toward the front substrate. Ends of the conductive lines 101 extend to a predetermined area of the edge of the rear substrate thereby defining a bonding area 100. The driving circuit 11 and one end of the FPC 12 are mounted to the bonding area 100.
Referring also to FIG. 7, driving signals generated from a driving circuit board (not shown) are applied via the FPC 12 to circuit pads 102 that are embedded in the bonding area 100. The circuit pads 102 are elongate, parallel to each other, and perpendicular to the edge of the rear substrate. The circuit pads 102 are spaced apart from each other at regular intervals. One end of each circuit pad 102 is connected to a corresponding conductive line 101 or to a terminal pin of the driving circuit 11. Two cross-shaped first alignment marks 103 are symmetrically disposed on two opposite lateral sides of the plurality of circuit pads 102, respectively. The FPC 12 includes a plurality of conductive fingers 122 and two second alignment marks 123. The conductive fingers 122 are parallel to each other and perpendicular to the end of the FPC 12, and are spaced apart from each at regular intervals. The second alignment marks 123 have the same shape as the first alignment marks 103. The second alignment marks 123 are symmetrically disposed on two opposite lateral sides of the plurality of conductive fingers 122, respectively. A distance between the two second alignment marks 123 is equal to a distance between the two first alignment marks 103.
Referring also to FIG. 8, in assembly, the second alignment marks 123 are precisely aligned with the first alignment marks 103 respectively, so that the conductive fingers 122 are precisely coupled with the circuit pads 102. Then the conductive fingers 122 are pressed against the circuit pads 102 at a temperature of 100 degrees Centigrade for 2 to 5 seconds. By this process, the FPC 12 is electrically connected to the circuit pads 102, and the driving signals can be transmitted to the display panel 10 via the FPC 12.
However, the conductive lines 101 adjacent to the edge of the display panel 10 have to be bent around the first alignment marks 103 so as to correspondingly connect with the circuit pads 102. Thus a distance between bend portions of each two adjacent conductive lines 101 is reduced. Short circuits are particularly liable to occur between the bend portions. Therefore the reliability of the connection between the display panel 10 and the FPC 12 may be rather poor. In addition, the bend portions need extra area at the bottom of the display panel 10. Accordingly, an area of the display panel 10 available for displaying is reduced.
What is needed, therefore, is an FPC that can overcome the above-described deficiencies. What is also needed is a display device employing such FPC.